fn main() {
    let _immutable_binding = 1;
    let mut mutable_binding = 1;
    println!("Before mutation: {}", mutable_binding);

    // Ok
    mutable_binding += 1;
    println!("After mutation: {}", mutable_binding);
    // notice: there is no ++ operation in rust
    // mutable_binding++;
    // ^if we compile this line, compiler will report:
    // Rust has no postfix increment operator

    // Error! cannot assign a new value to an immutable variable
    // _immutable_binding += 1;
    // ^ comment out this line, to pass compilation
}